Cyclic trisiloxanes or cyclotrisiloxanes can be generally described as ring structures containing six atoms in which three silicon atoms alternate with three oxygen atoms. These compounds are readily differentiated from higher cyclic siloxanes by the fact that they possess appreciable ring strain. Specifically, the nominal ring strain for hexamethylcyclotrisiloxane has been calculated as ˜2.5 kcal/mole, compared to ˜0.24 kcal/mole for octamethylcyclotetrasiloxane. This difference facilitates a number of ring-opening reactions. Of particular importance is the ability of cyclotrisiloxanes to undergo living AROP (anionic ring-opening polymerization), see C. Frye, J. Org. Chem., 35, 1308; (1970); J. Goff et al., “Living Polymerization Routes to Siloxane Macromers and Higher Order Silicone Structures,” Progress in Silicones and Silicone-Modified Materials, S. Clarson, Ed., Chapter 5, 59-78 (2013).
The ability to control precise functionality, particularly at high molecular weights, is a primary benefit of living anionic polymerizations. It is generally recognized that the kinetically driven AROP provides better structural control than equilibrium polymerization and is less subject to substituent effects (substitutions on the silicon atoms) that affect equilibrium. It is of great interest in silicone polymer chemistry to introduce alkyl ethers, particularly structures designated as poly(ethylene oxides) or PEGs, onto the silicon atoms of the polymer backbone. The ether structures can act as sites which introduce hydrophilicity into silicone polymers. In the area of living anionic polymerization, the practical ability to introduce alkyl ethers in a controlled manner has been limited by the unavailability of cyclotrisiloxanes such as (methoxyethoxyethoxypropyl)trimethylcyclotrisiloxane. Practical synthesis of members of this class of compounds has not been reported. Thus, there is a need for strained cyclic siloxane systems containing alkyl ethers, in particular alkyl polyethers.